The present invention relates to a method for establishing communication links to and from access lines which belong to line termination units of subscriber access units of an exchange in a switching system comprising a number of exchanges and to each of which access lines subscriber terminal equipment, in particular telephone, fax, PC and/or other communication equipment can be connected, wherein the subscriber access units are firstly connected to one another by means of a connection arrangement and are each connected to a central controller which, based on the dialing information fed to it from the line termination units, permits the establishment of the communication links concerned via a central switching unit, and wherein connections between access lines of line termination units which belong to one and the same subscriber access unit or to line termination units of subscriber access units which, on the basis of the connection by means of the aforementioned connection arrangement, are adjacent and can be established directly in the subscriber access unit concerned or between the subscriber access units which by means of the connection arrangement concerned are connected to one another and are adjacent to one another without the involvement of the aforementioned central switching unit.
A method of the type designated above brings with it in switching systems currently in use, like the switching system launched commercially under the name EWSD, a relieving of the load on the central switching unit since tie-line traffic within the respective subscriber access unit or between adjacent subscriber access units which in respect of remote network access are also designated remote switching units, takes place under the control of the central controller without the involvement of the central switching unit. Over and above these connection options, no connection options are possible here between different access lines of the various subscriber access units.